Process for grading materials.



H. K. HITGHGOGK.

PROCESS FOR GRADING MATERIALS.

APPLIGATION FILED JULY 19, 1907.

2 SHEETS-SHEET 1.

INVENTOR Patented Sept. 21, 1909.

WITNESSES H. K. HITGHCOGK.

PROCESS FOR GRADING MATERIALS.

APPLICATION FILED JULY 19, 1907.

2 SHEETS-SHEET 2.

WITNESSES INVENTOR T UNITED STATES PATENT OFFICE.

I HALBERT K. HITCHCOCK, F TARENTUM, PENNSYLVANIA.

raocnss r03 GRADING MATERIALS.

Specification of Letters Patent. Patented Sept. 21, 1909.- Application filed Jul 19, 1907. Serial 110,884,687.

To all whom may concern:

Be it known that I, HALBERT K Hrron- 000K, a citizen of the United States, residing at Tarentum, in the county of Allegheny and State ofPennsylva'nia, have invented certain new and useful Improvements in 'Processes for Grading Materials, of which the following is a specification.

My invention relates to a process for separating material comprising particles having different physical characteristics into grades each of which' includes those particles having similar physical clraracteristica'and is applicable for exampleto the grading of material used as abrasives such as are employed in the grinding of glass or other substances, the binders used in ceramics and in fact to the grading of any material what'- ever which it is desired to separate into gra es. The invention has for its primary objects; the provision of a process wherein the separation into the various grades may be accomplished more conveniently and economically-than has heretofore been the case; to providena process'wherein the radin is accomplished with greater certainty t an has heretofore been possible, and in which none of the useful material is wasted; and finally, to provide a process which may be carried out by a compact and inexpensive apparatus at high rate of speed.

Certain forms of the apparatus whereby the process may be practiced are shown in the accompanying drawings, wherein one rm of the apparatus,

Figure 2 isa longitudinal section through a second form of the a paratus, and

Figure 3 is a longitu inal section through a third form of the apparatus, in which apparatus the process is adapted to be carried on continuously. O

For the sake of definite illustration, the apparatus is'shown and hereafter described as a plied to the grading of abrasives used in g as grinding, but it will be understood that the rocess is ap licable to the grading of any. nely divided material whatsoever, and that the scope of invention is not limited to the grading of any but is coincident with t estatment of invention and claims. Y Briefly stated, the process consists in passing a stream of water of constantly decreasing -velocity' upwardly and densitg Figure '1 is a longitudinal section through articular material,-

velocity of the liquid counterbalances the normal downward velocity of the particles of material, when falling in the liquid, and they are held in suspension at predetermined positions in the tank, which positions depend upon the upward velocity of the liquid, and the resistance to the liquid of the articles and the weight of the particles. he particles in which the ratio of the weight to the resistance is lar esttake the lowest positions, as the normal ownward velocity of a parti- 'cle through the liquid depends upon this ratio, which ratio in particles of the same sha e increases with the size of the particles. pact particles thus come to a position of equilibrium in a stratum in the bottom of the tank where the upward velocity is greatest, while the. other particles arrange themselves in .a series of strata, the ratios of weight to the resistance of the particles composing whichstr'ata decrease as the distance from the bottom of the tank increases.

Referri first tothe form of apparatus shown in Figure 1 for carrying out the process as applied to the grading of abrasivps used in glass grinding operations, 1 is a separating tank of the conical form shown and is provided with outlet pipes 52, 3, 4 and 5 at various levels, and the overflow pipe 6 near the top, 7 is the pit to which the mlxed water and abrasives from the grinding tables are conducted, 8 is the admission pipe extending into thepit at its lower end and provided with a cut-ofi' valve 9, 10 is a Water pipe leading from the pressure. main, which pipe is provided with the valve 11, 12 is a steam plpe having its lower end upwardly curved for injecting steam into the admis sion ipe and securing a flow of water from the it 7 through the tank, 13'is a hydrometer or aging the density of the mixture in the tan'l r, which hydrometer is preferably guided on. a cross support 14, and 15 are valves for controlling the flow from the pi es 2, 3, 4 and 5. In order to give a lateral agltation to the tank, which agitation under certain conditions romotes the action of the ap aratus, an electro magnet 16 is pro- 'vided t rough the coils of which an alternat ing current is sent to secure a movement of the armature 17 which is secured to the tank. The vibration im arted prevents the cohesion of the partic es and as a result secures he larger, denser and more comweight to resistance in the liquid are difi'erent from those of the constituent particles. And furthermore, such vibration prevents the particles from lodging or sticking to'the sides of the tank and permits of a tank with the divergin walls at an angle greater than the angle of repose for the substance in the liquid. The located to suit requlrements and give the desired volumes of liquid in the strata lying between the various pipes.

The process may be carried out in a number of ways with the above described apparatus one of which is'as follows. The pit 7 being filled with a mixture of material and Water, steam is admitted to the pipe 12', thus sending a stream of water upward through the pipe 8 and tank 1, and the particles'gradually rise until they reach the positions at which they are in equilibrium. These positions of equilibrium lie at the points at which the upward velocity of the water from the pipe 8 equals the velocity at which the particles would normally fall through the fluid if there were no upward flow. It will be seen that the velocity of flow through the tank decreases as the distance from the bottom of the tank increases, because of the increased area of the tank at the higher levels and also from the greater tendency of the larger particles to reduce the interstitial spaces, this in itself increasing the velocity of flow at the lower levels, and that such velocity is inversely proportional to the area of the said interstitial space at any given point. As the falling velocity of a particle depends upon the ratio of its weight to the surface which is exposed to the resistance of the water, and this ratio for materials of substantially the same specific gravity increases with the weight of the particles, the particles of material composing the contents of the tank will arrange themselves in aseries of grades with the average size and weight diminishing andthe interstitial area increasing as. the distance from the bottom of the tank increases. The inflow of water through the pipe 8 is continued until a certain predetermlned density of the mixture in the tank as indicated by the hydrometer is secured,-at which time the valve 9 is closed and the valve 11 opened admitting water under pressure from the main, which flow of water from the main is necessar to maintain the particles already in equilibrium at their proper height, and to carry to their proper positions the finer particles last carried in from the pit and mixed through the tank, it being understood that the flow of water with the valve 11 open is preferably the same as that which occurs when the valve 9 is open, in which case one flow takes the place of the other. The upper valve 15 is opened and the contents of the stratum above the pipe 5 is withdrawn through such pipe 5,

pipes 2, 3, 4 and 5 are after the next lower stratum is drawn off, and then the next until the tank is emp= proper Stratification of the various grades of material is repeated. It will be apparent that all of the material in any one stratum is not of exactly the same degree of fineness, but that the difference between the finest and coarsest material in the stratum is fixed between redetermined limits. The proportions 0 the tank and the flow through the pipe 8 are so arranged that none of the material, which it is desired to save, will pass out of the overflow 6, which overflow 6 carries ofi, however, the mud which is mixed with the material or particles too fine for use, and the surplus water introduced into the tank.

The foregoing is only one species of the broad. process involved. If desired, the material to be graded may be introduced at the top of the tank and the grading secured by means of the flow of water from the pipe 10 in which case the valve 9 is, of course, closed. It is also not essential that the grades be withdrawn by means of the plurality of pipes as the entire contents of the tank may be withdrawn from the bottom pipe and the mixture used as Withdrawn, or

may be withdrawn in successive volumes,

each of which volumes is carried to a different receptacle and settled. When all the liquid is withdrawn from the bottom pipe, the particles are preferably held in suspension during the withdrawing operation by means of a flow from the pipe 10.. It will also be apparent that various means other than that shown might be used for elevating the material securing the upward flow of fluid through the tank and for securing the lateral agitation of the tank, and in fact the agitating means is in many cases omitted.

In Figure 2 I have shown another form of apparatus for carrying out the process, the

difl'erence over the apparatus of Figure 1' dation, in the material, the tank must be made of considerable height as indicated. Asthe particles of material at the upper levels are farther apart than at the lower levels and the quantity of material perunit volume correspondingly less as the distance from the bottom of the tank increases, the withdrawing pipes 2, 3, 4' and 5 are prefesa,441

form of apparatus for carrying out the process, which apparatus is. designed for a continuous operation wherein the flow of the mixture of material and water into the bottom of'the tank is continuous andthe outflow from the various discharge pipes is also continuous instead of intermittent as in the structure shown in Figure 1. In this construction the pipes 2 3*, 4 and 5 are extended into the tank and provided with small openings 20, so that a very small percentage of the li uid flowing in at the bottom of the tank is discharged at such discharge openings, the bulk of the liquid pass-,

. ing out at the overflow pipe 6 This is obvionsly desirable in order to prevent an undue 1 proportion of the finer material from being diverted. during its upward movement and being discharged at the opening below its position of equilibrium. The steam injector 12 is provided asin the other forms of the apparatus, but as the operation, is continu ens no valve is necessary in the adm ssion tube 21, and no separate water inlet is neces- 'sary, Iii-this form of apparatus the character of the original mixture, has little or no effect upon the varitnis grades, as the proportion of material to water is so small that any changein interstitial space and resultant change, in velcclty due to a change H1 the character material is very slight.

having t1 s described my invention and v illustrated use, I claim as new desire to secure by Letters Patent is the following a 1. The process of grading finely divided material in suspension in a liquid, which consists in projecting a relatively small volume of the liquid containing such material substantially vertically at decreasing s eed through a relatively large deep body 0 liquid free of obstruction capable of detaining the material in a state of rest, and withdrawing the desired grades directly from such relativel large deep body of liquid at different leve s, while maintaining the same densities of'the mixture not withdrawn during the withdrawin operation. 2. The process 0% grading finely divided material in suspension in a liquid, which consists in projecting a relativelysmallvolume of the liquid pontaining such material substantially vertically and continuously at decreasing speed through arelatively large deep body of liquid free from obstruction eration, and continuously withdrawing at difierent levels a volume of the mixture which isrelatively small as compared with the volume of the mixture projected upwardly. v j Y L ln testimony whereof l have hereunto si%ied my name in the presence of the two su scribed witnesses.

HALBERT K. HITCHCOCK. 

